Welcome to Astrosite Groningen.
On these pages you mainly find information, and a presentation of results,
on a number of astronomical subjects that we find most interesting.
Our main interests are comets and variable stars; therefore, emphasis will
be on the various aspects of observing these objects (charts, observations,
photographs). But we also plan to cover other topics, albeit only as an
aside, such as eclipses, and atmospheric phenomena like aurora and
noctilucent clouds, mainly by presenting a selection of our photographic
results. We hope you enjoy this site. We always welcome comments,
and suggestions for improvement. And feel free to contribute:
observations, images, whatever you want to share...

NEW! October 24, a file with comparison stars from APASS in the magnitude 10-15 range for the November 2018
moonless period can now be downloaded from the comp. stars section.

C/2017 O1 (ASASSN) past perihelion

This comet, discovered on July 19, 2017 by the ASAS-SN patrol operated at the Cerro Tololo Observatory in Chile, was apparently in a small
outburst at the time reaching 10th magnitude a few days later. Unfortunately it has hardly brightened since, and is now well past its peak of 9th magnitude.
It passed perihelion on October 14 at 1.499 AU and is very well placed for northern hemisphere observers over the coming weeks, moving slowly in Cepheus,
only 3-4 degrees from Polaris.

The (binned) image to the right is a single 3m (test) image obtained on October 15, starting at 22h25m UT, by Albert van Duin. He observed from
Burlage with his 40cm reflector.
The telescope was moved there recently from his backyard observatory in Beilen, and can now be operated remotely under much darker skies.

Undoubtedly more and better images to follow soon!

The second (binned) image, provided by Sandro Baroni from Milan, was obtained by Graziano Ventre on November 26 from Sormano, Italy.
Full details are shown on the image.

C/2015 ER61 (PANSTARRS) near the Pleiades

This comet, discovered in March 2015 as an asteroidal object of 20th magnitude by the PanStarrs survey, more than 2 years before perihelion
passage in May 2017 at 1.04 AU, peaked at 6th magnitude in April after a small brightness outburst while being best observable from the southern hemisphere.

In the meantime it is down to magnitude 13, but is easily located moving slowly near the Pleiades (M45).

The (binned) image to the right was provided by Sandro Baroni from Milan, Italy. It was obtained by Graziano Ventre in the night of 20 August 2017.
Full details are given on the image.Note the long thin dusttail!

C/2015 V2 (Johnson) brightening

This comet, discovered in November 2015 by J.A. Johnson as a magnitude 17 object in the course of the Catalina Sky Survey,
has been gradually brightening since, and is now well visible in binoculars at 7th magnitude, moving south through Bootes.
The apparition is very favourable for observers worldwide with perihelion near oppostion on June 12, 2017 at 1.637 AU, reaching its closest
distance to the Earth at 0.811 AU only a week earlier.

The (4x4 binned) RGBL image to the right was obtained in the night from 25 to 26 May by Emiel Kempen with a 25cm f/3 newtonian reflector
equipped with a SXVR-H18 CCD-camera.
It was composed from 59 120s exposures (10R,10G,9B,30L) taken between 21h52m and 00h54m under excellent conditions.
The image clearly shows, besides a fairly extended greenish coma, a bright dust tail and a faint gastail.

Over the coming week C/2015 V2 will continue to slowly brighten probably reaching magnitude 7 in the first weeks of June.

Comet 2014 Q2 (Lovejoy) at its brightest

This image shows this comet near its brightest at magnitude 4 and well placed for both Northern and Southern Hemisphere observers, moving
rapidly north through Taurus into Aries. It was taken by Albert van Duin from his observatory in Beilen on January 14 around 17h30m UT.
It is a stack of 9 10s-images with a modified Canon 5D MKII at ISO1600 equipped with a 50mm/f1.7 Pentax lens. This is a 4x4 binned crop of
the original image.

This image was taken early on January 20 by Jim Melka from Chesterfield, MO, showing quite a bit of detail in the gastail.
Further details are on the image.
Over the coming weeks this comet is expected to fade. However, it is still very favourably placed for Northern Hemispahere observers,
moving to high northern declinations, reaching +89 on May 30. By that time the brightness is probably down to magnitude 9-10.
[Update 25-01-2015]

Comet 2014 E2 (Jacques)

This comet is currently the brightest comet in the sky - being slightly brighter than 7th magnitude and well placed for Northern Hemisphere
observers - moving rapidly through Cassiopeia. The image above was taken by Albert van Duin from his observatory in Beilen, as a first test of
his new 290mm f/2,5 astrograph. It is a stack of 30 30s-images with a modified Canon 5D MKII taken on August 23 between 20h33m en 20h56m UT.
This is a 3x3 binned crop of the original image. The bright star near the comet is 32 Cas.
On the same evening this comet was imaged by Emiel Kempen in Hoogeveen with a 25-cm f/4 Newton equipped with a SBIG ST10XME.
His RGB composite of 5 30s images in each colour can be viewed by clicking here. [August 27, 2014]

On September 17 between 19h22m and 19h54m UT Albert van Duin imaged the comet again with the same equipment. The image above is a 2x2 binned crop of
a stack of 30 60s images. It is obvious that the comet is clearly past its prime, and is rapidly fading. [Update September 24, 2014]

Some personal memories of

Bill Bradfield (20 June 1927 - 9 June 2014)

It is with great sadness that I learned today of the passing away of Bill Bradfield, one of the greatest visual observers of the 20th century,
with 18 credited comet discoveries between 1972 and 2004.

I had the privilege of being a guest to his family twice, in 1983 and 1986, when he took ample time to discuss with me his searching technics,
showing his instruments and most of the locations Northwest and East of Adelaide from where he made his discoveries till then.
What struck me most, apart from his friendly and very modest character, was his meticulous planning and sheer determination to the 'job'.
When I suggested once that he should also try to observe and report visual observations of other comets, now that he was out there anyway
- in those days there were really very few southern observers - he politely declined. That would take time, better spent on covering more sky!

Our third and last meeting was in December 2002 in his new home in Yankalilla, where he moved to around 1995, when I visited him with Georg Comello
after observing the total solar eclipse of December 4. At the time he had made 17 discoveries, but was still searching for comets despite living
now in a poorer climate, and not to forget the stiff competition of the new automated CCD searches of LINEAR, NEAT and the like since the mid to
end nineties.
His perseverence was rewarded 15 month later, when after a nearly nine year drought he finally found his 18th and last comet C/2004 F4
(Bradfield), which developed into a very fine naked eye object for northern hemisphere observers after perihelion passage.
Unfortunately, he never found a really great comet, but this probably is the one that came closest.

Bill, you will be in my heart for the rest of my life.May you rest in peace.

Reinder Bouma, Groningen, 16 June 2014.

Naked eye Nova in Delphinus

On August 14.584 Koichi Itagaki of Yamagata, Japan, using a 18-cm reflector + CCD found a 'new' 6-7th magnitude object in Delphinus;
24 hours earlier nothing down to magnitude 13 had been visible, so this was very likely a nova. Indeed, early spectroscopy showed that this
was a classical nova, still on the rise.

The image to the left, a crop of a 68s exposure at ISO1600 with a Canon350D and 70mm lens, was taken by Edwin van Dijk on August 14 at
22h10m UT from Burlage, when the brightness was close to magnitude 6.0.
The next night the brightness had increased another magnitude, and it peaked near magnitude 4.5 or slightly brighter around August 16.5.
Thereafter a rather gradual fading set in.
By now (October 7) it has started to fade more rapidly, probably due to the formation of a dustshell around the nova.
Therefore, it is worth to further follow this object closely over the coming weeks!
In the meantime it has received the permanent designation V339 Delphini.

For Northern Hemisphere observers it is the brightest nova since V1494 Aquilae which peaked near magnitude 4.0 in early December 1999...

[Updated October 7, 2013.]

Bright comet 2011 L4 (PANSTARRS) in evening sky

This comet, after performing nicely for southern hemisphere observers en route to perihelion on March 10 at 0.302 AU from the Sun,
was observable from the northern hemisphere both near the end of evening twilight and near the start of morning twilight in early April.
The image above was taken by Albert van Duin from Ewer, a hamlet some 20km NW of Groningen, on the evening of April 2. It is a stack of
30 30s exposures with a 200mm f/2.8 lens on a Canon 5D MkII set at ISO800, taken between 19h57m and 20h17m UT, showing the comet near M31.

Four days later, on April 6, Emiel Kempen imaged this comet during our semi-annual starparty at Burlage under excellent conditions.
The image above is a stack of 16 20s exposures, taken between 20h26m and 20h33m UT with a 25-cm f/2.9 reflector equipped with a Canon 40D
camera, set at ISO400.

Over the last couple of weeks observing conditions have gradually improved now that it is a circumpolar object for most of the northern
hemisphere. However, after reaching first magn. around perihelion its brightness has decreased rather rapidly, and now it is down to 8th
magnitude. Because of the development of a nice wide fanning dusttail it is still a nice object for both visual and photographic observers.
[Updated 8 May.]

Bright Sungrazer 2012 S1 (ISON) at the end of 2013?

This comet was discovered by Vitaly Nevski and Artyom Novichonok with a 40-cm telescope as part of the ISON project as a virtual stellar magn. 19
object with unusual motion on September 21. It was confirmed on the following days by them and others as a clearly cometary object in larger telescopes
and thus received the designation C/2012 S1 (ISON).
It was soon realized, and the first orbit confirmed it, that this was a non-Kreutz sungrazer with perihelion at 0.012 AU on November 28, 2013.
Interestingly, the orbit is somewhat similar to that of the great comet of 1680.
A good summary of the events around the discovery can be found at the cometography website.

There has been a lot of speculation about the maximum brightness around perihelion, and some sources quote a magnitude between magnitude -10 and -15.
These numbers should be taken with more than the proverbial pinch of salt though. Objects with a small perihelion distance are very sensitive to the
brightness development within 1 AU from the Sun; with the same Ho (currently about 5) at 1 AU the difference in brightness at perihelion for this comet
is nearly 10 magnitudes if n is not the 'standard' 4, but only 2. Still, this comet will probably reach negative magnitudes when close to the Sun, and
will very likely be a spectacular object for Northern hemisphere observers postperihelion if it survives perihelion. Definitely to be continued.....

The most recent image to the right was obtained by Albert van Duin from his backyard observatory in Beilen, The Netherlands on March 12, 2013 using a
40-cm f/4.5 reflector, equiped with a QSI583 CCD. It is a stack of 4 180s exposures in 2x2 binning mode taken between 22h08m and 22h24m UT.
The comet is still a rather inconspicuous object, although already showing a short tail, but we expect this will change dramatically over the coming 8-9 months.

Images of three comets

The images to the right were obtained by Albert van Duin from his backyard observatory in Beilen, The Netherlands on October 10, 2012 using a
ASA 20-cm f/2.75 reflector, equiped with a QSI583 CCD, which automatically guided on the head of the comet.

168P/Hergenrother in outburst!

This comet was discovered by Carl Hergenrother in November 1998 in the early days of the Catalina Sky Survey as an inconspicuous 17th magnitude object.
It was duely recovered in 2005 and then received its permanent number 168P. Again, despite being favourably placed it remained rather dim.
The apparition of this year is about the most favourable possible with perihelion close to opposition, but based on its past performance it was not expected to become brighter than about magnitude 14.
So it was a pleasant surprise when visual observers picked it up in early September when most agreed it was about magnitude 12.5-13.
But the best was still to come.
We were quite surprised to find a very strongly condensed object on the evening of September 22, nearly a magitude brighter than three days earlier;
168P was clearly in the early stage of an outburst!
But more importantly, it continued to brighten over the full moon period, and in early October - when it could be observed again in a dark sky -
it was still very condensed and had further brightened to about visual magnitude 9-10, at least 4 magnitudes brighter than anticipated.

Now almost 3 months past perihelion 168P is clearly fading rapidly. It appears that the outburst , which (as images with large telecopes recently
clearly showed) was the result of a nuclear breakup, is largely over.
This recent image was obtained by Albert van Duin from his backyard observatory in Beilen, The Netherlands on December 13, 2012.
It is a stack of 10 180s exposures taken between 16h36m and 17h08m UT through a 40-cm f/4.5 Newtonian reflector, equipped with a QSI583 CCD
in 2x2 binning mode.
More images of this comet can be viewed here in our 168P image gallery.

[update December 23, 2012.]

Bright comet 2009 P1 (Garradd)

This intrinsically bright comet was discovered by Gordon Garradd in the course of the Siding Spring Sky Survey 2½ years ago,
in August 2009. It is now well past perihelion which occurred on December 23 at 1.55 AU from the Sun. Over the coming months it will still be a binocular
object, well placed for Northern hemisphere observers, after reaching a maximum of about magnitude 6½ in February 2012.

The most recent image to the right was obtained by Albert van Duin from his backyard observatory in Beilen, The Netherlands on March 22, 2012.
It is a stack of 30 120s exposures taken between 22h03m and 23h08m UT through a 40-cm f/4.5 Newtonian reflector, equipped with a modified Canon5D MkII set at ISO1000.

More images by Albert van Duin and Emiel Kempen can be viewed here in our C/2009 P1 image gallery.

[update March 23, 2012.]

The great Christmas comet 2011 W3 (Lovejoy)

This comet was discovered by Terry Lovejoy (Thornlands, QLD) as a 12-13th magnitude object om images obtained on 27 and 29 November.
After confirmation on December 1 by other observers a first orbit indicated that this was a Kreutz sungrazer, the first discovered from Earth since 1970.
However, it appeared that its absolute brightness was only marginally greater than that of the brightest sungrazers found in SOHO/LASCO images, so almost
nobody believed that this object would survive perihelion.

So, great was the amazement and exitement when after perihelion, on December 16.012, the comet re-emerged from behind the occultation disk of
the LASCO cameras as a bright stellar object, while the remnants of the preperihelion tail were seen drifting away at the other side of the Sun.
An excellent summary of the events around perihelion as seen by a multitude of solar observing satellites can be read at
Karl Battams' blog here.

Within a few hours a new tail started to grow, and a few days later earthbound observers in the southern hemisphere were able to see
the tail sticking out of the horizon in bright morning twilight.2
Observing conditions improved rapidly afterwards and the comet became a really spectacular sight in the days around Christmas when the Moon had
left the morning sky and the comet could be seen against a relatively dark sky before the start of twilight.
In particular the tail had the shape and high surface brightness so typical for Kreutz sungrazing comets, but the head was very inconspicuous,
and lacking a clear central condensation, rendering accurate astrometry virtually impossible.

The first image to the right was obtained by Rod Austin from New Plymouth, New Zealand on December 24, 15h08m UT.
It is a 75s exposure trough a 18mm lens at f/5.6 at ISO1600.

The second image was taken two days later, on December 26.71 UT, by Michael Mattiazzo from Castlemain, VIC.
It is a stack of 10 30s exposures at ISO800 with a Canon 300D and a 18mm lens. The tail can be followed over 38 degrees, although
its surface brightness is clearly fainter than two days earlier.

The two bright stars near the middle of both images are α and β Centauri, while Crux and the Coalsack can be seen near the top.

A series of images received from Graham Wolf shows that the comet could be well imaged with relatively simple digital cameras.
A selection of his images, taken near Turakirae Head - southeast of Wellington, New Zealand - with a Panasonic DMC-LS80 can be viewed by clicking on this image:

In the meantime this comet has virtually faded into the sky background. Maybe it is still possible to catch a last glimp from very dark
locations, but for most observers this object has gone.